Abstract:
Growth and production of chetin and chitosan of starch-degrading fungi were investigated. There fungal strains, aspergillus niger 5-82 and Setosphaeria monoceras 10-85 isolated from starch processing waster, and Aspergillus oryzae TISTR3018 used as a reference strain were selected for further studies based on the glucosamine yield and/or glucosamine content in the cell wall. The maximum glucosamine yield (0.81 g/L) was obtained from Aspergillus niger 5-82, while S.monoceras 10-85 and A.oryzae TISTR3018 had shown higher glucosamine content in their cell wall, i.e. 206.06 and 189.17 mg/gAIF, respectively. The optimal concentrations of soluble starch, as a carbon source, for the growth and the production of chitin and chitosan were varied from 4% for A.niger 5-82 to 6% and 8% for S.monoceras 10-85 and A.oryzae TISTR3018, respectively. In addition, urea had proved to be a sutitable source of nitrogen for A.niger 5-82 and A.oryzae TISTR3018. On the other hand, the growth as well as chitin and chitosan yield of S.monoceras 10-85 had increased significantly when 0.25% ammonium sulfate was used as a nitrogen source. The results demonstrated that A.oryzae TISTR3018 was superior in chitin production while S.monoceras 10-85 was proved as a promising chitosan producer. The production of chitosan by these two strains was enhanced in the modified starch medium supplomented with 0.025% magenesium sulfate. The maximum yields of chitin (7.98 g/L) and chitosan (557.75 mg/L) derived from A.oryzae TISTR3018 and S.monoceras 10/85 grown on the supplemented medium after four days of cultivation were abut 2-4 folds higher than those of the control starch medium. This implied that the increase of chitin and chitosan yields was a result of the increasing amounts of fungal growth as well as the chitin and chitosan contents in their cell walls.